Light emitting diodes (LEDs) devices are widely used in various applications such as indicators, signs, light sources, and other types of lighting. LEDs emit light when voltages are applied across a p-n junction. Different wavelengths of light can be generated using different materials by varying the bandgaps of the semiconductor layers and by fabricating an active layer within the p-n junction.
A phosphor material is usually added to change the properties of light generated by the LED. For example, monochromatic light provided by an LED can be converted to polychromatic light through the application of several phosphors, either in a mixture or several phosphor layers. The phosphors Stokes shift property shifts a shorter wavelength light to a longer wavelength. The perception of white light may be evoked by generating mixtures of wavelengths that stimulate all three types of color sensitive cone cells (red, green, and blue) in the human eye in nearly equal amounts and with high brightness compared to the surroundings in a process called additive mixing. A white light LED may be used as lighting, such as back lighting for various display devices, commonly in conjunction with a liquid crystal display (LCD).
The existing methods of forming a phosphor material on an LED device have not been entirely satisfactory in every aspect. For example, more efficient methods and designs that extract more of the light generated and improve light and color distribution continue to be sought. Accordingly, there is a need for an improved method for forming a phosphor material on an LED device.